The present invention relates to a sensor device for measuring an attitude, acceleration or gravitational field and its gradient components, said device including a spherical cavity which contains a sensor substance in the form of a fluid or some other inertial material having fluidic properties.
An accelerometer provided with a spherical cavity is previously known e.g. from U.S. Pat. No. 3,461,730. This prior known device produces an absolute acceleration value regardless of direction. Unlike this, a device of the invention can be used for sensing an acceleration as a vector quantity. The prior known device also does not include any indications for identifying the attitude of the device, while one of the fundamental features of the present invention is the identification of an attitude of the device.
As for the prior art, reference can also be made to publications U.S. Pat. No. 3,992,951 and EP Publication 0566130. The latter relates to a sensor for rotational motion, describing the principles of sensor elements or transducers which can be applied also in the present invention. In other words, the sensors may comprise piezoelectric transducers, capacitive membrane sensors and elongation strip sensors. Other types of sensors or transducers can also be used, as described in more detail hereinafter.
An object of the invention is to provide a sensor device, capable of determining the attitude of the device or the rate and direction of its acceleration 3-dimensionally. In other words, the sensor device must have an equal directionality in all directions to make it capable of sensing an acceleration vector, in addition to which the device also serves as an attitude identifier.
This object is achieved by means of the invention.
Some of the application areas for a sensor device of the invention are e.g. as follows:
in industrial manufacturing and robotics as attitude identifier or a triaxial sensor for linear motion (acceleration)
in navigation systems (inertial navigation) in land vehicles, water- and aircraft, in various self-controlled or self-navigated mobile devices
in so-called black boxes of vehicles (when the kinetic history of a vehicle is to be recorded)
in geophysics, geotechnique and in other areas of construction engineering e.g. as a triaxial vibration transducer, as an attitude sensor in drill holes, as a motion/attitude sensor for equipment towed by survey vessels, and as a sensor for gravitational field measuring equipment.